Tag Archives: sun-trap

Built to help control the indoor climate, it is enclosed by solid walls and solid gates made of a sandwich of fibre and polystyrene.
At times when free circulation of air is wanted, the gates can be latched open. That has the disadvantage that dogs and small children can pass in and out.
I have now made the control of air separate from the control of traffic by adding a wicket gate in each gateway.

The first photo (above) is a view of the courtyard as one would enter it from the west. Both main gates are open. The west wicket gate stands partly open, and the east wicket gate is closed.

West solid gate closed and wicket gate bolted open.

The second photo, taken from just inside the courtyard, shows the west main gate closed to prevent the flow of air. The wicket gate is fully open, as it would be in that case, secured there by its drop bolt.

Courtyard through east wicket gate

In the third photo, the courtyard is seen through the open east main gate and the bars of the closed east wicket gate.

These photos were taken on the 1st of August 2017 at 10:30 am. They show the courtyard receiving sunshine that passes over the roof of the house, as it does during winter mornings. Some sunshine is direct, some reflecting diffusely off the wall, and some reflecting brightly off mirrors of aluminium foil.

Two thermometer screens can be seen in the third photo. I am monitoring temperatures to find if the courtyard is affecting the indoor climate. As an experiment, I keep the main gates open or closed in alternate months. When gates were open in a particular month of the first year, they are closed in that month of the next year.

The wicket gates are made of welded, pre-galvanised steel tube in the style “Pool’nPlay Flattop”, powder-coated in white. They were supplied and installed in July 2017 by Bluedog Fences for $1793.

I have begun to warm the shady side of my house with reflected sunlight in winter.

Sun Mirrors Mar-17

This winter’s set-up.

The first photo shows the present temporary set-up, done on the 10th of March 2017. That is, soon after I had changed the house from its summer regimen (to keep cool) to its winter regimen (to keep warm).
As shown, I attached aluminium foil to the courtyard wall on the south boundary of my block. The foil forms mirrors that reflect winter sun onto the south wall of the house, the edge of the floor slab, the footings and some nearby concrete paths.
The mirrors are sheets of aluminium cooking foil (“Alfoil”) 300 mm wide, cut to 900 mm lengths. I attached the foil to the wall in vertical strips with double-sided tape. As the wall is 12.6 metres long, the total mirror area is 11.3 square metres.

Last winter’s set-up.

Sun Mirrors May-16

Last year, during April and May, I attached only 17 strips of foil 700 mm long in the same way. The total area then was 3.6 square metres. In that winter, the wind did a little damage, which I taped over. Much worse damage was caused by a magpie-lark attacking his reflection. By October, they were torn as shown in the third photo.

Bird Damage Oct-16

I repaired some of that damage, too, using builders’ foil, which is stronger. Early in November 2016, I removed all the foil. By then I wanted shade. not sunlight.

Effect of the mirrors

The white-painted courtyard wall reflects nearly all the sunlight it receives. However, this is diffuse reflection, going equally in every direction. Only a small part of it goes to points likely to warm the house.

Reflected Light May-16

The aluminium foil reflects in a specular (mirror-like) way, sending nearly all of the solar energy downward at the same angle that it arrived. Because the foil is wrinkled, these mirrors spread the beam of sunlight out to about twice the width of the mirror surface. It is still quite concentrated as can be seen in the last photo, which is lit mainly by reflection from the foil.

Light reflected from these aluminium mirrors is not aimed precisely at points where it would best warm the house. The mirrors are not mobile, and their location owes a lot to chance. Furthermore, the house shades the mirrors for parts of each day; different parts as the season changes.
However, I think the warming effect will be useful, and I hope to be able to measure it.

Related Topics

The mirrors are part of the Courtyard that I have described in posts and pages listed in “My House Page”.

I raised the question of mirrors to reflect sunlight in a thread titled “Reflective Film” on a forum of the Alternative Technology Association (Melbourne). (I posted as “Catopsilia”, my first post being the 15th from the top.)

This porch, which is a sun-trap in winter, is converted simply to a shaded breezeway for summer.
The porch is an upstairs outdoor room, open on three sides, at the west end of my house. With a Tallowwood deck and steel balustrade, it could be called a verandah or a balcony. I like to call it a talar, although it is not as grand as the talar of the Ali Qapu Palace, Isfahan.
For the colder part of the year, from March to October, the talar awnings are arranged as in the right photo. I fasten down the canvas awning on the south side to stop drafts, and I roll up the awning on the west side so I can enjoy the views. On sunny winter afternoons it is pleasant to have a late lunch there, with temperatures in the high twenties, several degrees warmer than the maximum in the thermometer screen.
For the warmer part of the year, from November to February, the awnings are arranged as in the left photo. The awning on the west side is fastened down against the intolerable heat of the afternoon sun. That also keeps the heat off the west wall of the house. The south awning is raised, to allow air to flow through, from south to north. When there is a breeze, it can be comfortable to sit on this porch even on very hot days.
By the use of cheap canvas awnings, this porch can make outdoor living pleasant in months when the climate here is too cold or too hot for it.

I have added a courtyard to my high-mass solar-passive house to improve summer cooling and winter heating.

Courtyard Wall Panels and Gates

The courtyard extends 13 metres along the south wall of the house. It is completely enclosed by a wall of white-painted polystyrene sandwich panels 1.8 metres high, with two gates of the same material.

By September 2015 trenches had been dug for the courtyard foundation, and by December it was complete.

Courtyard Trenches, West

Courtyard Trenches, East

Operation

This house is in BCA Climate Zone 4: Hot dry summer, cool winter. For comfort, it must be made very much cooler in summer and very much warmer in winter. The courtyard was built to help to achieve both results without the use of heaters or coolers.
In summer, it should ensure a supply of very cool air at night. In this house, cool air is drawn in to replace warm air that flows out the clear-story windows by the stack effect, assisted by fans. By day, the courtyard walls also block some solar radiation.

The Courtyard Through The Western Gate

In winter, the white courtyard wall reflects sunshine north towards the house, and re-radiates heat lost from the house wall back towards it.

More

New Post on Wicket Gates

In August 2017 I added a new post about wicket gates that were added to the solid gates in the courtyard gateways.

To invite discussion of how courtyards can affect indoor and outdoor climate of houses, I opened a thread “Courtyards for Climate Control” on the forum of the Alternative Technology Association (ATA) based in Melbourne.

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Back-dated monthly reports

Monthly and seasonal weather reports for Manilla now extend back more than nine years to June 2007. [Select ARCHIVES for the month following.]
"Manilla 3-year climate trends" graphs and reports extend back to May 2010 as consecutive months. Earlier graphs and reports are accessed in ARCHIVES September 2002, 2004, 2006, and 2008.